Abstract: The fatigue crack growth rates of powder metallurgy (P/M) superalloy FGH97 with different grain sizes, γ' phase sizes and Hf contents were measured at a 650℃ high temperature condition and compared with those of FGH95 and FGH96 alloys. The fatigue fracture behavior characteristic of FGH97 alloy in each stage was analyzed by the quantitative analysis method. It is found that FGH97 alloy with coarser grains has a lower fatigue crack growth rate. Reasonable match of secondary and tertiary γ' phases and Hf addition can get a higher fatigue life. Compared with FGH95 and FGH96 alloys, FGH97 alloy has the highest fatigue cack intiation resistance and exihibits the lowest fatigue crack propagation rate at high temperature.